Generally, the cylinders of an internal combustion engine are provided with a certain cooling means or cooling circuit to cool peripheral walls of the cylinders. This is because by cooling the peripheral walls of the cylinders, it is possible for the pistons of the internal combustion engine to smoothly reciprocate in the cylinders so as to slide along the surface of the liner of the cylinders. However, cooling of the peripheral walls of the cylinders often results in the occurrence of such an inconvenience that a part of the air-fuel mixture adjacent to the inner surface of the cylinders is quite susceptible to cooling via the peripheral walls of the cylinders, even after ignition of the air-fuel mixture. Therefore, even after the completion of the combustion of the air-fuel mixture, some amount of unburned or incompletely burned gas is left in the cylinders. Consequently, at some moment in the subsequent exhaust stroke of the pistons, the unburned or incompletely burned gas is discharged out of the cylinders together with the completely burned emission gas from the internal combustion engine.
In order to prevent any amount of an air-fuel mixture from being left unburned or incompletely burned, there has already been proposed a method of employing particularly shaped combustion chambers wherein a squish of a part of an air-fuel mixture fed into the cylinders is created during the compression stroke of the pistons of an internal combustion engine. The squish of the air-fuel mixture is forced to stream along the inner walls of the combustion chambers of an internal combustion engine. Thus, the stream of the squish of the air-fuel mixture forcedly causes all of the air-fuel mixture, which stagnates in a region of each combustion chamber adjacent to the peripheral wall, to move away from that region toward the center of the combustion chamber. The stream of the squished air-fuel mixture also assists in the creation of a swirl of the air-fuel mixture within the combustion chambers at the end stage of the compression stroke of the pistons. As a result, further mixing of the air-fuel mixture is promoted, so that a very homogenized air-fuel mixture is produced prior to the commencement of the combustion stroke of the pistons. Therefore, when the homogenized air-fuel mixture is ignited, quick flame propagation occurs in the cylinders. As a result, the speed of the combustion of the air-fuel mixture is greatly increased compared with an internal combustion engine having no squish and swirl creative combustion chambers.
An object of the present invention is to provide an internal combustion engine provided with squish and swirl creative combustion chambers having a novel shape compared with that of combustion chambers which have already been proposed, so that performance of an internal combustion engine is appreciably enhanced due to the simultaneous accomplishment of the cleaning of emissions from the engine and of an increase of the axial torque delivered from the engine.
Another object of the present invention is to provide combustion chambers of an internal combustion engine of which the shape is in a specified dimensional range determined by experiments which were conducted by the present inventor for the purpose of reducing the emission of unburned hydrocarbon components from an internal combustion engine and of increasing the engine output power.